Your average Nebraska cornfield looks peaceful enough. But there's a battle out there.

Sunrise to sunset, every growing season day, corn and weeds compete for essential sunlight. Stakes are high. The winner grows strong and productive. The loser produces less.

Farmers spray, till and manage fields to give corn an edge over yield-robbing weeds, but some of their longtime tools are in danger. Recent federal legislation may result in a phaseout of many common corn herbicides. Farmers need crop protection alternatives.

What if corn carried characteristics that boosted its competitiveness against weeds? Corn that could tolerate more weeds without sacrificing yields or suppress weed seed production would need less herbicide.

University of Nebraska Weed Scientist John Lindquist is working to identify important weed-beating characteristics. He hopes this research helps corn breeders identify weed-competitive genetic traits and provides information to help farmers boost corn's advantage.

After studying corn-velvetleaf competition for light in the field and simulating this interaction on computer, Lindquist has some solid clues about characteristics advantageous in the struggle for light.

"I think we have substantial evidence that there are characteristics that can be modified to improve corn competitiveness for light," the Institute of Agriculture and Natural Resources researcher said.

For two years, Lindquist grew two modern corn hybrids and two old hybrids popular in the 1940s under different velvetleaf infestation levels to compare plant characteristics, yields, light interception and other factors. He used new and old hybrids because their significantly different characteristics, such as height and canopy structure, made it easier to identify differences.

While the modern hybrids yielded far more than the older varieties, Lindquist measured relative yield to determine corn competitiveness. The old-timers generally were more weed tolerant, yielding relatively closer to their maximum potential with weeds present.

The best weed-competing corn plants shared several key characteristics, all related to corn's ability to shade velvetleaf. The most weed competitive hybrids had: greater leaf area, or more leaf area relative to ground area; greater leaf height; and higher leaf area, or more leaves high in the corn canopy.

Canopy closure, or how quickly corn leaves overlap to shade out weeds, also is important, Lindquist found.

"Bottom line, if you have things really crowded in, whichever species gets more of the area to absorb light will be better off," he said.

Lindquist found the most competitive hybrids tolerated roughly three times more weeds than the least competitive hybrids before reaching the point where herbicide treatment was economically justified.

"Basically, if you have a hybrid out there that competes well with weeds, you can have more weeds without hurting yield and weeds may produce fewer seeds," he explained.

Lindquist plugged findings into a computer model he's adapting to simulate corn-velvetleaf competition, which he's refining to improve accuracy. He'll also factor in how nitrogen fertilizer and water influence light competition.

Accurately modeling a cornfield's environment is complex but important, Lindquist said.

"Part of the reason for using models is to identify relationships that can improve weed management decision support software like WeedSOFT," Lindquist said. Farmers, consultants and others use this IANR-developed software to aid weed management decisions. Adding weed competitiveness information would let users explore how changes such as plant population or row width might improve their corn's competitiveness and use it in an integrated weed management approach.

Lindquist used standard 30-inch rows in these studies but thinks 15- or 20-inch narrow rows could improve corn competitiveness. He hopes to find funding to study narrow- row and high-population corn.

A USDA National Research Initiative grant helped fund this research.

- Vicki Miller

Researching corn-velvetleaf competition may help identify weed-competitive characteristics to boost corn's advantage over weeds.

IANR Weed Scientist John Lindquist grows old and modern corn hybrids and velvetleaf in the greenhouse as part of his research on corn-weed competition.

Lindquist measures velvetleaf in a research plot. Researchers grew a plot of velvetleaf to collect baseline information about how the troublesome weed performs in the absence of competition from corn.